I. Field of the Invention
The present invention relates to fluid systems for controlling the movement of an unequal displacement fluid cylinder and, in particular, the present invention relates to a closed-loop, hydrostatic system which is used to drive an unequal displacement cylinder.
II. Description of the Prior Art
Heretofore, numerous fluid systems have been employed for controlling the rate of movement of hydraulic motors and, in particular, a fluid system disclosed in my U.S. Pat. No. 3,653,208 issued on Apr. 4, 1972, discloses a closed-loop, hydrostatic system in which the output of a variable displacement pump is selectively directed at various rates to the opposite sides of a piston within an equal displacement fluid cylinder. There are a variety of applications when it is desirable to have a piston with only one piston rod. In such systems the effective pressure responsive areas on the opposite sides of the piston are unequal, and thus the volume of fluid to and from the opposite sides of the piston is also unequal. As a result, fluid cylinders having unequal displacements are not suited for closed-loop systems, as in closed-loop systems the fluid to and from the fluid pump must be substantially equal. A substantial advantage of a closed-loop system over an open-loop system is the availability of dynamic braking of the fluid cylinder in the closed-loop system.
It would therefore be desirable to provide a closed-loop fluid system which has all of the advantages as described in the fluid system disclosed in my issued Pat. No. 3,653,208 but which will drive an unequal displacement fluid cylinder and provide dynamic braking therefore.